of the outdoor recreation demand will 
be accounted for by recreationists 
taking shorter trips close to home. 
5. The number of people participating 
in nonconsumptive wildlife recreation, 
in both warm and cold water fishing 
and in migratory bird hunting, is 
expected to rise over the next 5 
decades. 
6. In general, domestic demand for 
metallic minerals and precious metals 
will continue to increase, but demand 
for any given metallic mineral is likely 
to be highly variable and dependent on 
technology and the evolution of end- 
use markets. 
7. Changes in global climate can 
significantly affect the productivity, 
health, and diversity of forest and range 
ecosystems. 
Population (millions) 
350 
300 
250 
Basic Assumptions About 
Future Determinants of 
Demand and Supply 
In the future, as in the past, demands 
and supplies of renewable resource 
products will be determined largely by 
growth in population, income, and 
economic activity; technological and 
institutional changes; energy costs; 
capital availability; and levels of 
private and public investments in 
forest, range, and water management, 
utilization, and research. 
Population 
In the past 5 decades, the population of 
the United States increased by over 100 
million people, to some 242 million in 
1986, the base year for demand and 
supply analyses (fig. 2, app. table 1). 
Projections by the Wharton 
Econometrics Forecasting Associates 
using Bureau of the Census 
assumptions about future population 
Population —_ 
Ls 
200 
150 
100 
50 
0 
1925 1940 1955 
1970 1985 2000 
Figure 2—United States population and gross national product, 1929-86, with projections to 2040. 
to 
demographics indicate that population 
will continue to grow, to about 333 
million in 2040. The population 
assumptions are the middle series 
projections developed by the Bureau of 
the Census, except that net immigration 
is assumed to be 750,000 people per 
year rather than the 450,000-person 
assumption used in the middle series. 
This adjustment in the immigration 
assumption is to account for net illegal 
immigration. 
Economic Activity and Income 
Economic activity, as measured by the 
official gross national product in 
constant dollars (1982 dollars net of 
inflation and deflation), increased more 
than fivefold in the past 5 decades and 
reached $3.7 trillion in 1986. In this 
period, there have been major 
GNP (§ trillion 1982) 
20 
15 
10 
2015 2030 2045 
